The present invention relates generally to refresh of shared cryptographic keys, and more specifically to refresh of a secret key which is shared between a plurality of servers for implementing a cryptographic protocol over a network.
Protecting information is essential in the digital economy. A common way to protect data is to use cryptographic algorithms to process the data in some way, but it is then necessary to protect the secret cryptographic keys which are used in such algorithms. An increasingly popular technique is to distribute (secret share) keys between a plurality of servers which can perform operations with a shared key in a distributed fashion to collectively implement some cryptographic protocol. Cryptography offers a very rich body of protocols for such operations. Sharing a secret key enhances security because more than one server must be subverted by an adversary for the key to be compromised. Some systems also offer so-called “proactive security”, whereby a secret key can be refreshed by periodically re-sharing the key among the servers. Proactive security can be realized by letting the servers engage in an interactive refresh protocol to re-compute their key shares.